1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a magnetic recording medium, and more particularly, to a magnetic recording medium that can reduce magnetic noise generated by magnetic domain walls.
2. Description of the Related Art
It is generally known that perpendicular magnetic recording achieves higher recording density than longitudinal magnetic recording. Accordingly, the perpendicular recording technology is adopted in most hard Disk Drives (HDDs) to achieve high recording densities today.
In perpendicular magnetic recording, the magnetization of bits of data is aligned in a direction perpendicular to the plane of a corresponding recording medium. Such perpendicular magnetic recording is performed using a double-layered perpendicular magnetic recording medium, which includes a ferromagnetic layer and a soft magnetic underlayer (SUL), and a pole head. The SUL, which is inevitably used due to the magnetic characteristics of the pole head, is disposed under a magnetic recording layer and guides a magnetic flux that adversely results in noise being generated by magnetic domain walls.
Various methods have been proposed to reduce noise generated by magnetic domain walls. Among the methods, there is a related art method of reducing noise generated by magnetic domain walls by forming a recording medium having a multi-layered underlayer structure and establishing an exchange coupling between underlayers. Another related art method is to prevent the formation of magnetic domain walls due to the exchange bias of a ferromagnetic layer by forming the ferromagnetic layer under an underlayer. Another related art method is to prevent the formation of magnetic domains by forming a magnetic domain control layer under an SUL. Various other methods of reducing noise have been suggested, but so far none have managed to address the problems of noise brought about by increasing recording densities of perpendicular magnetic recording mediums.